Method for Making a Transition between Polymer Grades

Abstract

The present invention relates to a method of transition between polymer grades in a polymerisation process comprising polymerising at least one monomer in at least a first reactor and a second reactor connected to each other in series, wherein the monomer feed in the first reactor is maintained essentially constant during the transition.

1 - 8 . (canceled) 
     
     
         9 . A method of transition between polyolefin grades in a polymerisation process comprising:
 polymerising at least one monomer in at least a first reactor and a second reactor connected to each other in series, wherein olefin monomer is fed into the first reactor at an essentially constant rate during a transition between the first reactor and the second reactor.   
     
     
         10 . The method of  claim 9 , wherein the olefin monomer comprises ethylene. 
     
     
         11 . The method of  claim 9 , wherein the first reactor and the second reactor comprise loop reactors. 
     
     
         12 . The method of  claim 9 , wherein the feed of monomer into the first reactor is changed by at most 5% in relation to an average monomer feed in the first reactor of the transition during the transition. 
     
     
         13 . The method of  claim 9 , wherein the feed of monomer into the first reactor is changed by at most 2% in relation to an average monomer feed in the first reactor of the transition during the transition. 
     
     
         14 . The method of  claim 9 , wherein the polymerization occurs in the presence of a Ziegler-Natta catalyst.